Detectives are keeping an open mind about whether the same gang is behind a series of raids on veterinary surgeries across the region.
Methadone and ketamine variants that could be fatal to humans are among the substances that have been taken in burglaries across two different counties.
Concerns sparked by the incidents are so severe that Public Health England has been notified.
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Thieves hit three surgeries in three hours in Cheshire on October 14.
The first saw a car - but no drugs - stolen from a practice on Chester Road in Hartford at around 8.56pm.
At 10.32pm two or three people broke into a surgery on Ditchfield Road in Widnes, stealing drugs before fleeing in a waiting getaway vehicle.
An hour and six minutes later, a surgery was targeted on Victoria Road in Runcorn. Nothing was taken in that raid.
In a public appeal - and warning - following the incidents, Inspector Rob Balfour said: “Public Health England have been informed. The drugs that were taken from the surgery are designed for the use in animals and are fatal if taken, so I’d strongly advise that if you are offered Dolethal, or a ketamine called Anesketin, or methadone called Comfortan - do not take it.
"These particular drugs are incredibly dangerous in the wrong hands and you will be putting yourself at considerable risk.
"We’d advise not taking any illegal drugs, but we understand some will, which is why we are taking this opportunity to warn the public."
Last week, a gang targeted a practice in south Liverpool, stealing a "large quantity of drugs and cash".
At around 8.10am on October 29, officers were called to Medivets on Green Lane in Mossley Hill to reports of an overnight burglary
Detective Inspector Debbie Tipton said: “It’s absolutely vital that whoever stole these drugs understands that human consumption can have serious or fatal effects.
"Likewise, if you have any information as to who was responsible or have been offered any stolen drugs come forward immediately and we will ensure that the person or persons involved are brought to justice."
Cheshire Police has confirmed no arrests have been made in connection with its investigation and told the ECHO it is keeping an open mind over whether the incidents are linked.
A spokeswoman did say that neighbouring forces had been notified.
They are known to include North Wales Police, which issued its own warning as the force called on veterinary surgeries to "review their security arrangements and ensure key holders' contact details are updated with [their] relevant security monitoring company".
*Anyone with information can call their local police force on 101 or contact Crimestoppers, anonymously, on 0800 555 111
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